This invention concerns a spray nozzle of the type specified in the preamble to claim 1, especially for spraying water in a fire prevention system.
Spray nozzles have been available for a long time. They have harrow helical channels that open tangentially into a vortex chamber that is connected to a narrow coaxial nozzle orifice. Rotation of the flowing liquid medium such as water is induced by the helical channels. The rotational speed is increased greatly along the radial path inward to the narrow coaxial nozzle orifice, so that as the water leaves the nozzle orifice it is flung outward due to the centrifugal forces prevailing at that point, thus forming a spray mist that spreads out essentially in a spray cone.
One disadvantage of this spray nozzle is that there is very little spray mist inside the spray cone, thus forming an area where there is little or no spray, especially at the center of the spray cone, so the fire extinguishing effect of the spray mist is much lower there.
East German patent DD 141,626 discloses a spray nozzle having a housing in which a first nozzle part is mounted. A first vortex chamber is formed between the first nozzle part and an inside wall of the housing. A first helical channel for supplying water is provided on the outside of the first nozzle part, opening tangentially into the first vortex chamber at a point remote from the axis of the vortex and having a first outlet orifice coaxial with the axis of the vortex. A second vortex chamber is formed between an inside wall of the first nozzle part and a second nozzle part arranged inside the first nozzle part, and a second helical channel for supplying water is provided on the outside of the second nozzle part, opening tangentially into the second vortex chamber at a point remote from the axis of the vortex and having a second outlet orifice coaxial with the axis of the vortex. When this spray nozzle is used, some water flows through the helical first channel to the first outlet orifice, so a spray mist in the firm of a first spray cone is formed under the spray nozzle. In addition, water also flows through the second helical channel to the second outlet orifice, so a spray mist is produced in the form of a second spray cone under the spray nozzle. The second spray cone has a smaller cone angle than the first spray cone, so the interior of the first spray cone is filled with a spray mist by the second spray cone and therefore an extinguishing effect is also achieved in the interior of the first spray cone.
One disadvantage of the known spray nozzle consists of the fact that its design is complicated due to the second nozzle part arranged inside the first nozzle part as required to produce the second spray cone, so the known spray nozzle is expensive to manufacture.
When assembling the known spray nozzle, first the second nozzle part must be screwed into the first nozzle part and then the first nozzle part is screwed into the housing. Thus, several steps are involved in the manufacture of this spray nozzle. This is time consuming, thus further increasing the cost of manufacturing the known spray nozzle.
Since the second nozzle part is arranged inside the first nozzle part, it has small dimensions, so the cross section of the second channel provided on the outside of the second nozzle part is also small accordingly. There is thus the danger that the second channel might become clogged due to the penetration of dust, etc. As a result, the second spray cone produced by the second nozzle part is formed inadequately or not at all, so the fire extinguishing effect of the spray nozzle is impaired. In addition, the width of the spray cone of the second swirl nozzle is rather small.
East German patent DD 245,825 A1 discloses a spray nozzle consisting of a hollow nozzle body with a break-away angle of 120.degree. at the outlet orifice of the nozzle head into which a nozzle insert part having spiral grooves on the outside and a hollow screw on the inside is inserted, where the nozzle insert in the hollow body of the nozzle leaves open a rinsing space where the water enters into a rotating decompression phase while at the same time there is a build up of pressure in front of the outlet orifice, and after flowing through the outlet orifice, a water cone is formed that produces a dispersion effect at the break-away angle of the nozzle head, thus improving the spray pattern by reducing the droplet size. Due to the rotation of the water in the rinsing space, the water is distributed in the form of a spray cone at the outlet orifice of the nozzle head. Since all the droplets are subject to the prevailing centrifugal force, a conical space that is essentially free of droplets is formed inside the spray cone. Thus, when this spray encounters a surface to be extinguished, only a ring of the surface is actually sprayed, but the inside of the ring does not receive any spray. Therefore, this known swirl nozzle has a very low fire extinguishing effect.
French patent 473,630 discloses a spray nozzle of the type in question, where the swirl chamber is designed in a trumpet shape and is sealed off by a wall in the wide intake area where there is a slot through which water enters the swirl chamber with a velocity component in the circumferential direction. This water forms a layer along the inside wall of the trumpet-shaped swirl chamber and flows along it to the tapering part of the swirl chamber, leaving as a spray cone because of the rotational component of the velocity.
At the center of the wall sealing off the trumpet-shaped swirl chamber there is a short nozzle out of which a stream of water enters the swirl chamber coaxially, leaving a hollow space in most of the swirl chamber between this central stream and the flow running along the inside wall of the swirl chamber. This bundled coaxial stream passes through the constricted part of the swirl chamber, with the rotating flow extending outside this bundled stream. The outer part of the bundled stream is rotated by entrainment, so its components are distributed to form a spray cone when leaving the tapered part of the swirl chamber, while the inside part of the bundled stream leaves the swirl chamber as a stream that is largely unaffected. This yields a fire extinguishing pattern with the bundled stream at the center next to a conical space on the outside that is largely free of spray mist, while a ring-shaped spray range extends toward the outside again. Therefore, this known spray nozzle does not have a good extinguishing effect, and furthermore there is an undesirable concentration of fire extinguishing water at the center.
The object of this invention is to make available a spray nozzle of the type in question that does not have the disadvantages of the known spray nozzle, that has a simplified design and is inexpensive to manufacture and assures reliable operation.
This object is achieved by the teaching characterized in patent claim 1.
The idea on which this invention is based consists of the fact that instead of a second inner swirl nozzle, there is a second channel that is coaxial with the axis of the vortex of the swirl chamber and a pressure gradient is produced in the direction of flow upstream from the second outlet orifice so the water flowing through the second channel is distributed to form a spray cone in the transition to a lower pressure range.
The spray mist produced in this way is distributed in the interior of the spray cone leaving the swirl chamber, so the desired fire extinguishing effect is also achieved inside this spray cone. Furthermore, the spray mist leaving the second outlet orifice has a higher velocity and thus also a greater spray width.
The second channel may be formed by a continuous recess that runs in the longitudinal direction of the nozzle part and is easy to produce. The spray nozzle according to this invention is thus simple and inexpensive to manufacture.
According to an embodiment of this invention, the enlarged area is formed downstream from a narrow portion of the cross section of the second channel as seen in the direction of flow. In this embodiment, the reduction in cross section and the widened portion following it form an orifice where a great pressure gradient develops, so the water is distributed to form a spray mist especially effectively.
According to another embodiment, the enlarged area is formed by a conical wall area of the second channel. In this embodiment, an especially simple way to produce the second channel is by producing a bore with gradations in diameter, where the reduction in cross section in the direction of flow is preferably designed with incremental stages.
In another embodiment of this invention, a nozzle part is arranged in the housing with the first channel on the outside and the second channel in the center.
Due to suitable dimensions of the second channel, especially the enlarged area and/or the reduction in cross section, the shape and droplet size of the spray mist leaving the second outlet orifice can be influenced within a wide range, so spray characteristics of the spray nozzle according to this invention can be influenced in a wide range.
Furthermore, the spray characteristics can be influenced through a suitable choice of the distance between the first outlet orifice and the second outlet orifice in the direction of flow. The distance between the second outlet orifice and the first outlet orifice can preferably be adjusted.
It is also possible to design the enlarged area and/or the narrowed portion of the cross section so they can be adjusted.